To add a link to text when editing a page, highlight the text which you want to turn into a link, or place the cursor where you want to insert the link.
Alternatively, click “Insert Link” on the toolbar, or use the shortcut Control-K in Windows, or Command-K on your Mac.
In the “Insert Link” dialog, you can search for content within your Confluence instance with “Search” or by selecting “Recently Viewed.” Click on “Files” to link to an already attached file or upload a new one. Under “Web link” you can enter a web page or email address to link to, and by clicking on “Advanced” you can insert a link to a new page or an anchor on the page you are currently editing.
After selecting the target of your link, click insert.
Alternatively, type an open bracket [ and then start typing the name of the page or attachment. The auto-complete suggests targets for your link.
You can also enter a URL directly on the page. Confluence automatically turns it into a link, and if the URL is a page in the current Confluence instance, the page name will automatically be used as the link text.
Watch our Video #87 of the Video Tutorial Series “Learn Atlassian Confluence” or check this page of Atlassian’s documentation for more information on this subject.
You can also check this answer about links.